Method of making grinding wheels



June 5, 1956 A. BLOCK 2,749,224

METHOD OF MAKING GRINDING WHEELS 2 Sheets-Sheet 1 Filed DBC. l5, 1954 ALECK BLOCK INVENTOR.

HIS ATTORNEY `lune 5, 1956 A. BLOCK 2,749,224

METHOD OF MAKING'GRINDING WHEELS Filed Dec. 15, 1954 2 Sheets-Sheet 2 ALECK BLOCK INVENTOR.

HIS ATTORNEY lthe interior structure;-

,Unifed Safes Parent ,2,749,224 METHOD F MAKINGVGRINDING WHEELS Aleck Block, Culver City, Calif., assignor to Merit Products, Inc., Culver City, Calif., a corporation of Caliornla Application December 15, 1954,`Serial No. 475,512

Claims. (Cl. 51-293) This invention relates to a large diameter abrasive grinding wheel and to an improved method of making thev same.

ln the manufacture of abrasive grinding wheels which are formed of a plurality of flexible strips or leaves of abrasive material, it is desirable to form a wheel which is simple to remove and replace when the abrasive becomes x force resulting from the speed at which the outer circumferential edge of the leaves is traveling. f Many buffers and grinders with which such wheels areused cannot be slowed down to a reduced speed and others are often not operated at a yslow speed, making it necessary that the wheel should have the greatest possible resistance to separation of the leaves while the wheel is in use. f

It is an object of my invention to provide an abrasive grinding wheel which successfully satisfies these requirements.- In the manufacture of such a wheel, I have found it desirable that one or more circular rings be used to hold Atheleaves in place, since adhesive alone will not resist the increased forces tending to pull the leaves from the wheel.

In essence, my invention `contemplates an abrasive grinding wheel formed by assembling a plurality of abrasive leavesin circular form, burning a circular groove in the opposite side edges ofthe assembled leaves, filling the grooves with liquid adhesive and mounting a ring in the grooves, the adhesive causing the leaves and rings to adhere together to provide a unitary assembly which will satisfactorily resist the forces tending to pull the leaves from the ring.

The use of a heated member such as Van electrode to burn the circular grooves in the abrasive leaves provides at least two distinct advantages. The rst is that burning is much `easier and better than using an abrasive or die to cut the grooves, since a cutter is quickly dulled by the abrasive material on the leaves which are being cut. The

other advantage is that the burning provides a better bond between the adhesive, leaves and ring to provide a stronger construction than would otherwise be possible. Further explanation of the latter advantages is set forth later in the specification of this application. v v Another object of my invention is toprovide a stronger and better large diameter grinding `wheel which can, at the same time, be manufactured and sold economically for widespread sale and use. e Y p e y y My invention also contemplates such other objects, advantages and capabilities as will later more fully appear and which are inherently possessed by my invention.

While l have shown in the accompanying drawings a preferred embodiment of my invention, it should be under-stood that the same is susceptible of modification and change without departing from the spirit of my invention. Referring to the drawings, Fig. l is 4a. top planview of my abrasive grindingA wheel partly broken away to show "ice Fig. 2 is a detailed sectional view showing a portion of my wheel in use, the adhesive being omitted from the illustration;

Fig. 3 is a greatly enlarged view of a leaf after the groove has been formed, showing how the libre structure of the leaf is affected by the burning of the groove;

Fig. 4 is atop perspective view of burning the grooves in the wheels.

A preferred embodiment which has been selected to illustrate my invention comprises an abrasive grinding wheel 10, which is formed of a plurality of rectangular leaves 1l, some or all of which are coated on one side thereof with suitable abrasive material. The inner ends of all of the leaves are attached by adhesive to a strip of cloth 12, which is in turn attached by adhesive to a circular center core 13, which is preferably formed of cardboard. The leaves 11 extend radially from the entire circumference of the core i3 to provide a complete circular wheel.

A substantially semi-circular groove 14 is formed in the sides of the leaves 11 concentric with core 13, but slightly larger in diameter. Such a groove 14 is formed on each side of the wheel 10 by applying a circular electrode 15 to the assembled wheel, the electrode being suitably heated by induction or high frequency heating. The electrode 15 is mounted on a ceramic foundation, and is provided with electrical wires which are connected to a suitable source of electrical supply for heating the electrede. The electrode is heated by methods known in the art to a temperature which will burn through the edges of the leaves 11 to form the grooves 14.

This method of forming a groove 14 is preferable to the use of abrasives or other cutting implements, since such abrasives or cutters are soon dulled by the abrasives on the leaves and must be sharpened or replaced, while the heated electrode is unaffected by the abrasive particles on the leaves and can satisfactorily burn the grooves in the leaves without requiring sharpening or replacement.

In burning the groove 14, the electrode 1S causes the portion of the leaves 1l adjacent the groove 14 to be partially burned. The portion of the leaves which was formerly within the groove is, of course, completely burned away. The portion of the leaves directly adjoining the edge of the groove is highly burned or charred, leaving only a few of the fibres of the leaves. The adjacent portions are substantially progressively less burnt back to the point where the leaves are unaffected by the burning of the groove.

The areas thus aii'ected are, of course, necessarily irregular, and are not clearly defined. For purposes of illustrating the operation of my invention, however, a limited area adjoining the groove is separated into zones. The first zone, which is marked A, is directly adjacent to the edge of the groove and contains few fibres. The second zone, which is marked B, contains a limited number of fibres. fi`he third zone, which is marked C, contains a large number of fibres. The fourth Zone, which is marked D, represents the intact leaf, containing all of its fibres. Such zones would not, of course, exist if the groove were cut with an abrasive or cutter. Thus, the present invention is readily distinguished because of the gradation in the fibre density within the edge surface of the groove.

After the groove has been burned in the leaves, it is filled with an adhesive, which is preferably vinyl glue. The vinyl glue not only fills the groove, but penetrates into the partially burned portions of the leaves adjacent the groove. In doing so, the liquid adhesive merges with the remaining fibres of the leaves to a decreasing extent as it passes through the zones from A to D. The result is thatl the inside of the groove holds pure glue, while zone A comprises a substantial amount of glue with a small amount of fibre mingled therewith. Zone B com- `3 prises a lesser amount of glue and a larger amount of fibres, to provide greater bonding and intermingling of the glue and leaves. Zone C comprises still less glue, with ya greater amount of fibre. Zone D comprises the leaves with only such glue `as can penetrate the entire leaf.

Regardless of the type of adhesive which is used, the action of the electrode in removing some but not all of the fibres from the area surrounding the groove results in a stronger bond being formed between the clue and the leaves. This feature of the invention is p :lai-ly important when adhesives of the vinyl or vinyl-polyester variety are employed with the invention. Such adhesives, when not reinforced by fibrous material, do not possess the same high strength they have when used in conjunction with fibre reinforcingmaterial. Thus, a bond is obtained which is stronger, `because the r ing lib-res of the leaves intermingled with and reinforce the adhesive. The advantages of this type of juncture are not limited to the adhesive of the specic categories indicated, but are also found with other resinous adhesives, such as phenolic derivatives, area formaldehyde compositions, or epoxy resins. Frequently` a small amount of carbon will be found attached to the individual fibres within the zones A. B and C. With many of these latter types of resins, this small amount of carbon merely serves as a filler for the resinous composition.

After the groove has been filled with adhesive, a circular ring ,ld is placed in the groove. The ring 16 is preferably formed of metal and is substantially equal in diameter across to the electrode 15, but is smaller' in cross-sectional diameter so that it tits properly within the groove. 'the relationship between the groeve .iii and ring 1-5 is preferably such that the top of the ring 16 is substantially flush with or very slightly beneath the top edge of the groove 14.

vt'lwn the ring is placed in the groove, tends to push apart the libres in zone n in much the same manner in t a common t shion gives when pressed. The fibres iin zone A and possibly son-ie or all of zone B then become bonded to thc ring by the adhesive without there bcizig any zone of substantially pL adhesive between the fibres of the leaves and the ring. Thi. provides a greater urea of direct contact between the ring and the leaves than would normally be ac ved if the ring were placed directly against the edge of a groove formed by conventional g inding other means, since such :in c s would have substantially the same fibre density as that found within the intact leaves.

ln addition to penetrating into the portions of the leaves adjacent the grooves, the liquit hesive also preferably penetrates between the leaves themselves adjacent the grooves and from the grooves to the inner edges of the leaves to provide the strongest possible bond and to provide a substantially rigid core which extends from the rings to the inner ends of the leaves.

A pair or" vulcanized fibre f 'ips 17 are then attached on cach of the wheel by glue. The inner diameter of the strips corresponds to the diameter of core i3 and the outer diameter of strips i7 is greater than that of the groove i4 so that the strips 27 conn letely cover the ring 16 and the glued portion of the wheel.

This assembly comprises my replaceable and discardable abrasive "finding wheel. lt should be noted that the fibre strips 'i7 conceal the rings i6 and glue filled groove i4 from sight and that the unit is easily handled or shipped. The leaves are separrte y handled and the user does not even know that the r .gs exist.

ln use. the nbre strips 17 are reinforced by metal ilauges 1S and have a pair of mounting plates to prevent displacement of the rings from the grooves.

While any suitable device may be used to effect the burning of the grooves, l have shown in Fig. 4 of the drawings one structure which will operate satisfactorily. ln this device, which may be mounted on a table or other fiat surface, a hollow square base 19 is provided with a centrally disposed opening in which is mounted a ceramic foundation 20 having an upstanding circular portion 21. Surrounding the circular portion 21 is the circular cleo trode l5, which is suitably connected by wires not shown in the drawing to a source of electrical energy so that it can be heated to a suitable temperature.

A circular holding member 22 is disposed directly above the circular portion 21 and electrode 15. Holding member 22 is attached to one end of an arm 23, which is vertically reeiproeally mounted on an upright stand 24. A coil spring 25 normally maintains arm 23 in the position shown `in the drawings. Downward pressure on a lever arrn 26 will move holding member 22 downwardly toward circular portion 21, overcoming the pressure of coil spring 2S. A duct 27 is provided to remove fumes resulting from the burning operation. A hose 28 also removes fumes from above the wheel.

in use, a wheel 10 is -placed so that its core 13 surrounds circular portion 21. The holding member 22 is then lowered by operation of lever arm 26 to hold the wheel 10 tightly against the circular electrode 15 to burn the groove 14. he wheel is then reversed and the operation repeated to form the groove in the opposite side of the wheel. lf a substantial quantity of char is present within or adjacent to the groove, it can be removed by a wire brush. The brush may be operated by hand or may be .lowered into the groove while the wheel is mounted on a rotating turntable.

l claim:

l. The method of for/ming an abrasive grinding wheel comprising combining a plurality of leaves to form a circular wheel, at leastsome of said leaves having an abrasive surface thereon, applying a heated circular member to each of the side edges of said wheel, the application of said heated member completely burning a portion of said leaves to form a pair of grooves in the sides of said wheel, said heated member partially burning the portions of said leaves adjacent to said grooves to destroy a substantial amount of the fibres thereof in the area directly adjacent to said groovesand a substantially progressively lesser amount of the fibres in the areas farther away from saidgrooves, filling said grooves with liquid adhesive, said adhesive penetrating into the partially burned areas of said leaves adjacent said grooves to provide an effective intermingling of the remaining fibres of said leaves with said glue, Vand mounting a circular ring within each of said grooves, said rings and leaves being bonded together by said adhesive.

2. The subject matter of claim l, and filling the arca between the ends of said leaves with adhesive to provide a lsubstantially rigid core extending from said rings to the inner ends of said leaves.

3. The method of forming kan abrasive grinding wheel comprising combining a plurality of leaves to form a circular wheel, atleast some of said leaves having an abrasive surfaee thereon, applying an electrically heated circular electrode to each of the side edges of said wheel,

Athe application of said electrode completely burning portionsof said leaves to forma pair of grooves in the sides of said wheel, said electrode partially burning the portions of said leaves adjacent to said grooves to destroy a substantial amount of the fibres thereof in the area directly adjacent to said grooves and a substantially progressively lesser amount of the fibres in the areas farther away from said grooves, filling said grooves with liquid adhesive, Vsaid adhesive penetrating into the partially burned areas of said leaves adjacent said grooves to provideaneffective intermingling of the remaining fibres of Said leaves with said glue, and mounting a circular ring within each of said grooves, said rings and leaves being bonded together by said adhesive.

4. Themethod olf-forming an abrasive grinding wheel comprisingcombiningaplurality ofleaves to form a circular wheel, at least some of said leaveshaving an abrasive surface thereon, applying an electrically heated circular electrode to each of the side edges of said wheel, the application of said electrode completely burning a portion of said leaves to form a pair of grooves in the sides of said Wheel, said electrode partially burning the portions of said leaves adjacent to said grooves to destroy part of the bres thereof in the area adjacent to said grooves, filling said grooves with liquid adhesive, said adhesive penetrating into the partially burned areas of said leaves adjacent said grooves to provide an effective intermingling of the remaining fibres of said leaves with said glue, and mounting a circular ring within each of said grooves, said rings and leaves being bonded together by said adhesive.

5. The method of forming an abrasive grinding wheel comprising combining a plurality of leaves to form a References Cited in the tile of this patent UNITED STATES PATENTS 2,164,800 Davis July 4, 1939 2,259,475 Koether Oct. 21, 1941 2,651,894 Leggett Sept. 15, 1953 2,678,523 Leggett May 18, 1954 

3. THE METHOD OF FORMING AN ABRASIVE GRINDING WHEEL COMPRISING COMBINING A PLURALITY OF LEAVES TO FORM A CIRCULAR WHEEL, AT LEAST SOME OF SAID LEAVES HAVING AN ABRASIVE SURFACE THEREON, APPLYING AN ELECTRICALLY HEATED CIRCULAR ELECTRODE TO EACH OF THE SIDE EGES OF SAID WHEEL, THE APPLICATION OF SAID ELECTRODE COMPLETELY BURNING PORTIONS OF SAID LEAVES TO FORM A PAIR OF GROOVES IN THE SIDES OF SAID WHEEL, SAID ELECTRODE PARTIALLY BURNING THE PORTIONS OF SAID LEAVES ADJACENT TO SAID GROOVES TO DESTROY A SUBSTANTIAL AMOUNT OF THE FIBRES THEREOF IN THE AREA DIRECTLY ADJACENT TO SAID GROOVES AND A SUBSTANTIALLY PROGRESSIVELY LESSER AMOUNT OF THE FIBRES IN THE AREAS FARTHER AWAY FROM SAID GROOVES, FILLING SAID GROOVES WITH LIQUID ADHESIVE, SAID ADHESIVE PENETRATING INTO THE PARTIALLY 